[ io 7 ] 



and the contrary. Either limb of the Sun may he 

 ufed in either obfervation ; but it will be moft con- 

 venient in general to make the Sun appear againft 

 the fky, and not againft the fea ; and then the ob- 

 jects appearing inverted through the telefcope, the 

 Sun will appear loweft, and the horizon higheft. 

 The obferved altitude is to be corrected for dip, re- 

 fraction, and Sun's femi-diameter, as ufual. 



In taking the diftance of the neareft limbs of the 

 Sun and Moon, whether by the fore or back-obfer- 

 vation, having firft fet the index to the diftance 

 nearly, by the help of the Nautical Almanac, and 

 brought the Moon to appear anywhere on or near 

 the diameter of the field of view of the telefcope, 

 which bifects the interval between the wires, give a 

 fweep with the quadrant, and the Sun and Moon 

 will pafs by one another j if in this motion the 

 neareft limbs, at their neareft approach, juft come 

 to touch one another, without lapping over, on or 

 near any part of the diameter of the field of the te- 

 lefcope which bifects the interval between the wires, 

 the index is rightly fet; but if the neareft limbs 

 either do not come to meet, or lap over one another, 

 alter the index, and repeat the obfervation till the 

 neareft limbs come to touch one another properly. 

 This method of obferving will be found much more 

 eafy and expeditious than without the wires, fince 

 in that cafe it would be neceflary to make the limbs 

 touch very near the centre of the telefcope, but here 

 it is only neceflary to make them do fo anywhere on 

 or near the diameter of the field of the telefcope 

 which bifects the interval between the two wires. 



P 2 The 



